Assessing biophysical variable parameters of bean crop with hyperspectral measurements

Abstract

Recently high spectral resolution sensors have been developed, which allow new and more advanced applications in agriculture. Motivated by the increasing importance of hyperspectral remote sensing data, the need for research is important to define optimal wavebands to estimate biophysical parameters of crop. The use of narrow band vegetation indices (VI) derived from hyperspectral measurements acquired by a field spectrometer was evaluated to estimate bean (Phaseolus vulgaris L.) grain yield, plant height and leaf area index (LAI). Field canopy reflectance measurements were acquired at six bean growth stages over 48 plots with four water levels (179.5; 256.5; 357.5 and 406.2 mm) and tree nitrogen rates (0; 80 and 160 kg ha-1) and four replicates. The following VI was analyzed: OSNBR (optimum simple narrow-band reflectivity); NB_NDVI (narrow-band normalized difference vegetation index) and NDVI (normalized difference index). The vegetation indices investigated (OSNBR, NB_NDVI and NDVI) were efficient to estimate LAI, plant height and grain yield. During all crop development, the best correlations between biophysical variables and spectral variables were observed on V4 (the third trifoliolate leaves were unfolded in 50 % of plants) and R6 (plants developed first flowers in 50 % of plants) stages, according to the variable analyzed

Economically optimal water depth and grain yield of common bean subjected to different irrigation depths

“…The result obtained here agrees with that of Monteiro et al (2012), who observed the same behavior in this parameter for irrigated beans, increasing from 8.73 to 17.05 pods plant -1 with water depths of 179.5 and 357.5 mm, and decreasing to 12.63 pods as the water depth increased to 406.2 mm. Torres et al (2013) observed that the number of pods per plant was highest with the replacement of 100% ETc, 10.37 pods per plant, for the cultivar Pérola, studying different replacement levels and different soil covers.…”

Correlations between spectral and biophysical data obtained in canola canopy cultivated in the subtropical region of Brazil

“…The higher shoot dry matter (Table 1) (Jensen, 2009;Monteiro et al, 2012;Ponzoni et al, 2012). The vegetation activity includes leaf area index (LAI), green coverage, chlorophyll content, green biomass, Table 1.…”

“…It is noteworthy that the red and near infrared bands are widely used to calculate vegetation indices because they are the most well correlated with green biomass. Monteiro et al (2012) correlated the LAI with hyperspectral data in a bean crop and reported negative correlations between the LAI and the bands at the visible wavelengths, and positive bands at the near infrared wavelengths.…”

Índices de vegetação simulados de diferentes sensores na estimativa das variáveis biofísicas do feijoeiro

“…Para esta variável, o modelo que melhor se ajustou aos índices de vegetação foi o geométrico. Monteiro et al (2012) …”

“…Para estimar o IAF, as medidas de radiação difusa, acima e abaixo do dossel do feijão, foram coletadas no início da manhã em 01/11/2007, em todas as parcelas, no estádio fenológico R6 (floração), conforme Gepts & Fernandéz (1982). O estádio R6 foi caracterizado como o melhor estádio da cultura para estimar as variáveis biofísicas, por apresentar a maior quantidade de biomassa verde das plantas (Monteiro et al, 2012).…”